1. Technical Field
The apparatus and methods are related to equipment and processing for seismic exploration for oil and gas, and more particularly to acquiring and processing seismic data.
2. Description of the Related Art
Reflection seismology is a branch of seismology that uses reflected seismic waves to produce images of the Earth's subsurface. Using seismic exploration methods which include noting the time it takes for a reflection to arrive at a receiver, it is possible to estimate the depth of the feature that generated the reflection.
Seismic exploration for hydrocarbons is conducted using a source of seismic energy and receiving and recording the energy generated by the source using seismic detectors. On land, the seismic energy source may be a controlled explosive charge or another energy source having the capacity to import impacts or mechanical vibrations at or near the earth's surface. Seismic waves generated by these sources travel into the earth subsurface and are reflected back from strata boundaries and reach the surface of the earth at varying intervals of time depending on the distance traveled and the characteristics of the subsurface material traversed. The return waves are detected by the sensors and transduced into electrical signals which are recorded for subsequent processing.
Normally, signals from sensors located at varying distances from the source are added together during processing to produce “stacked” seismic traces. In marine seismic surveys, the source of seismic energy is typically air guns. Marine seismic surveys typically employ a plurality of sources and/or a plurality of streamer cables, in which seismic sensors are mounted. Land surveys may be acquired with sources such as dynamite, accelerated weight drop or seismic vibrators. Sources and receivers may be positioned in a collinear fashion to record 2-D profiles or in an areal fashion to acquire 3-D data. By acquiring data at different times, the data may be formed into “4-D” data that may illustrate changes in the subsurface over time.
The process of exploring for and exploiting subsurface hydrocarbon reservoirs is often costly and inefficient because operators have imperfect information from geophysical geological characteristics about reservoir locations. Furthermore, a reservoir's characteristics may change as it is produced.
The time from mineral discovery to production may be shortened if the total time required to evaluate and explore a survey area can be reduced by reducing the time and equipment necessary for deploying to acquire geophysical data. Equipment that is autonomous or stand-alone and that doesn't need to be in constant communication with a a control center could represent a reduction in resources and an increase in data acquisition efficiency.
Seismic sensors and their associated autonomous seismic data acquisition unit equipment can be expensive to position, to use and to continuously maintain in field operations. Decreasing the unit cost of deployed seismic units is desirable.